The atom transfer radical polymerization of styrene and methyl methacrylate with FeCl2/iminodiacetic acid as the catalyst system in bulk was successfully implemented at 70 and 110 degreesC, respectively. The polymerization was controlled: the molecular weight of the resultant polymer was close to the calculated value, and the molecular weight distribution was relatively narrow (weight-average molecular weight/number-average molecular weight similar to 1.5). Block copolymers of polystyrene-b-poly(methyl methacrylate) and poly(methyl methacrylate)-b-poly(methyl acrylate) were successfully synthesized, confirming the living nature of the polymerization. A small amount of water added to the reaction system increased the reaction rate and did not affect the living nature of the polymerization system.